Also quoted: "In 'Against the Fall of Night' the human race has mysteriously regressed after a full billion years of civilization. Humanity is faced with the r

Also quoted: "In 'Against the Fall of Night' the human race has mysteriously regressed after a full billion years of civilization. Humanity is faced with the remnants of its past glories: for example, a network of roads and sidewalks that flow like rivers. Although physically possible, it is inexplicable from their perspective. Clarke's Third Law explains the source of our amazement as our limitation, rather than the impossibility of the technology." Another counter-argument to your quote is that "distinguished but elderly scientists" very publicly claimed it was impossible to fly, as late as 1904. Some even proclaimed this after the Wright brothers had done it. As for the amount of energy, that is an estimate based on this very early design hypothesis. It points us in the right direction to continue research, but does not necessitate there will not be much more energy efficient ways to power such a device.